Central american pair for standard 90 gallon.

  • We are currently upgrading MFK. thanks! -neo
Carpintis, Loisellei, Lyonsi, Salvini...many others would work. If you want that pair to fill the tank up, I’d go with Loisellei. Just note that you can have issues if the male decides to beat on the female.
 
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Its all about footprint, if you had said a 90 L (6ft) your options might be slightly more varied, but to me a pair that maxes out at 9" is as far as I would push the limit of a 90 standard. And even then I'd have a divider at the ready, to drop in, to protect the female.
The standard footprint (IMO) leaves out any Parachromis, or similar species, like grammodes, and also leaves out any of the Vieja genus.
Amatitlania, Thorichthys, or others of that less territorial temperament would be better choices (maybe a pair of bartoni).

And if it were me, I'd start with a group juvies (6-8) and allow them to determine their own pair. In that way, it will be obvious, and by letting them select on their own, that pair bond could be more tightly knit.
If you were to opt for the more bellicose species (like grammodes), also start with juives, but expect the pair to kill off any others that don't make the muster .
I had grammodes years back, bought half dozen 2" juvies, grew them out in a similar footprint tank to yours, by the time they were 4" a pair had formed, and killed off all others, they spawned 3 times, so I thought they were bonded enough, but the male killed the female one night.
Even 6 ft tanks are quite tiny compared to natural habitat for aggressive territorial types.
Most cichlids make 4 ft, a territorial boundary, and only break off chase at that point, so even a 6ft tank offers little extra space once a males territory has been determined.
 
What duanes duanes said.
 
Definitely agree that it’s all about foot print. That limits choices. I only mentioned grammodes because they are very slow growers. You rarely see them push 10” for a male. Maybe better for a solo than pair perhaps.
I agree smaller species would be a better choice. I would be hesitant to do a group of thorichthys in a 4’ tank. Only because of bioload-slightly crowded will mean constant water changes. If going this route I would lean more towards the smaller growing species.
H. Deppi pair would be nice. They don’t get too big and are beautiful.

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Most cichlids make 4 ft, a territorial boundary, and only break off chase at that point, so even a 6ft tank offers little extra space once a males territory has been determined.

Agreed, and IMO in captivity that boundary seems to increase. Less to worry about, such as predators, or larger/stronger rivals attacking from behind, in the confines of a glass box.

As an example, a much smaller typically aggro species, Tropheus sp., when conversing with Mark Young (at that time a collector & exporter living on the shores of Lake Tanganyika) he told me that in his experience dominant males would stop chasing at the 6-8ft mark, so he built all of his concrete vats 12 ft. End of serious aggression problems. This is with 4-5" fish!

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How about a pair of Nicaraguan cichlids? As beautiful as they are, you don't see too many on the boards.
 
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